Design of intelligent baby carriage control system based on 51 single chip microcomputer

Overall design
The intelligent remote-controlled music baby stroller consists of several parts, including the baby stroller intelligent control module, detection system, remote control module, display module, execution system, and music module.
(1) The baby stroller intelligent control system adopts an embedded system design, which can automatically run, process data, control and coordinate the work of each module. Users can observe and control each part of the baby stroller based on the development of this system. At the same time, the system can be controlled by a keypad or infrared remote control.
(2) The detection module is divided into sound detection, urine detection and temperature detection. The corresponding signals are given to 89C52 respectively for whether the baby wakes up, whether the baby is wet, and the milk temperature. Each detection module is controlled by the system.
(3) The remote control module adopts NEC standard infrared remote control, which can remotely control the playback mode of MP3 decoding, music effects, song selection, volume, and system time adjustment. Control and coordination of each module.
(4) The display part adopts LCD12864 liquid crystal screen display, which can display time, countdown time, bottle temperature, and humidity status.
(5) The actuator is divided into mechanical execution and sound execution, so as to more perfectly simulate the effect of people.
The overall structure diagram is shown in Figure 1.

2 Hardware Design
2.1 Hardware Structure
This paper selects Atmcl's STC89C52 chip as the control core of the controller to complete the data storage, communication and coordination of infrared, LCD screen, detection system, keypad and actuator.
2.2 Hardware Design of Intelligent Remote Control Module
The controller circuit design is mainly divided into the following modules:
(1) The peripheral circuit of STC89C52 includes power management, keyboard, LCD screen, etc.
(2) Design of remote control module and its circuit: This paper selects ordinary infrared transmitting and receiving tubes and adopts NEC standard encoding and decoding.
(3) Detection system and its circuit design: This system mainly detects three physical quantities: sound, temperature and liquid. The sound uses a triode amplifier circuit with an electret microphone as the signal source. The temperature is measured with an 18B20 temperature detection chip. The liquid measurement is a triode amplifier circuit with two probes as the signal source.
(4) Actuator: The mechanical mechanism is mainly driven by a high-power DC brush motor. The drive circuit with L298N as the core drives the motor, and the PWM generation circuit with 555 as the core drives L298N to achieve speed regulation.
2.3 Microcontroller pin settings
The microcontroller model used in this article is STC89C52, which has 32 operable I/O ports. After completing the system allocation, there are still I/Os that have not been operated, so there is no need to expand the I/O port. The I/O allocation is shown in Figure 2.

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2.4 Design of remote control module circuit
The remote control module adopts the common car MP3 remote control on the market. It can be seamlessly connected with the MP3 decoding module. The internal program is used to call its buttons to wirelessly operate the time, etc.
The remote control decoding adopts the central processor according to the NEC standard. NEC standard: The frequency of the remote control carrier is 38kHz (duty cycle is 1:3); when a key is pressed, the system first transmits a complete full code, and then transmits a series of simple codes after delay until the key is released and stops transmitting. The simple code repeats with a delay of 108ms, and the interval between the rising edges of each two guide pulses is 108ms. A complete full code is shown in Figure 3. Among them, the boot code is high level 4.5ms, low level 4.5ms; the system code is 8 bits, the data code is 8 bits, a total of 32 bits; data 0 is represented by "high level 0.5625ms + low level 0.5625ms", data 1 is represented by "high level 0.5625ms + low level 1.6875ms", a simple code = boot code + system code bit 0 inverse code + end bit (0.5625ms,) high level. Its timing and working principle are shown in Figure 3.

2.5 System power supply design
In view of the high power characteristics of this circuit, this paper adopts independent power supply design, which is divided into single chip working power supply, MP3 decoding module power supply, and motor drive power supply. The circuit is shown in Figure 4.

2.6 Motor control design
2.6.1 Motor drive circuit design
The baby carriage has two motors, which control the shaking of the baby and the opening and closing of the bottle respectively. The drive circuit with L289N as the core is used. The circuit is shown in Figure 5.

2.6.2 Design of motor speed control circuit
Considering that the motor is a high-power DC motor, the motor shape is fixed. It is unrealistic to control the number of magnetic poles to achieve speed control. The series resistor has a large current change due to its large workload. In summary, this article uses PWM waves to achieve motor speed control. There are two ways to generate PWM waves: software and hardware.
Solution 1: Through software, the required hardware adds A/D electrical conversion links and A/D conversion on the basis of the original 89C52.
Solution 2: Through hardware, the required hardware is the common 555 timer.
In summary, the latter is superior to the former in terms of program design and cost. Its design circuit is shown in Figure 6.

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2.7 Music module of baby carriage
This article uses MP3 decoding module for music playback and control. It can read MP3 files in USB, SD, and MMC cards, and supports FAT12 and FAT16 file systems. It supports MP1layer3, MP2layer3, and MP3layer3 version song files. Its principle is shown in Figure 7.

2.8 Design of detection circuit and infrared receiving circuit
The detection system of the baby carriage plays a vital role in this product. The main physical quantities detected are the temperature of the milk bottle, the crying of the baby and the liquid under the baby. The temperature of the milk bottle is measured by 18B20. In view of the high decibel and long duration of the baby's crying, a low-sensitivity sound trigger circuit is used to trigger the high and low levels to the central processor. At the same time, this design can also detect external noise with high decibels and long duration. The infrared circuit is mainly an infrared receiving tube. Its circuit is shown in Figure 8.

3 System software design
The system software is mainly divided into six parts. They are time, detection, infrared decoding, key detection, external output, and LCD12864 display. The system takes infrared remote control as the highest priority and monitors infrared signals at all times. Users can modify the time at will, including the duration after triggering. Through the research and development of this system, the expected goals have been achieved in practical applications. It provides great convenience for baby care.